棕色田鼠不同性别中R-spondin1基因的特殊表达

哺乳动物睾丸决定的诱导一般依赖于Sry基因,然而棕色田鼠指名亚种的Sry基因已经丢失,而棕色田鼠指名亚种雌雄个体依然有繁殖能力。我们在研究涉及性别决定的一些基因时,发现R-spondin1与性别决定有关。为了探讨R-spondin1在棕色田鼠中的性别决定中的作用,我们用RT-PCR检测R-spondin1在棕色田鼠性腺中的表达。研究结果表明R-spondin1仅在出生后不久的棕色田鼠指名亚种雌性个体的卵巢中表达,在出生后的棕色田鼠指名亚种雄性个体睾丸中未见其表达,这说明R-spondin1可能在棕色田鼠指名亚种卵巢发育中具有某种角色。     

Exclusion of Sall 4 as the sex-determining gene in the Mandarin vole Microtus mandarinus mandarinus

In previous studies, we have shown that the Sry HMG-box is absent in Microtus mandarinus mandarinus (M. m. mandarinus), suggesting that sex determination of M. m. mandarinus is independent of the Sry gene. We amplified a 312 bp fragment within exon 2 of the Sall4 gene in the mouse and M. m. mandarinus using polymerase chain reaction (PCR) and detected Sall4 using fluorescence in situ hybridization (FISH) technique. The probes for the Sall4 gene were labeled with digoxigenin using PCR and hybridized to chromosomes and interphase nuclei of the mouse and M. m. mandarinus. Our results suggested that Sall4 exists in the genome of male and female M. m. mandarinus, and the sequence within exon 2 of the gene is the same in the mouse and M. m. mandarinus. The results also showed that Sall4 is localized on chromosome 6 in M. m. mandarinus. As they are the sex chromosomes in M. m. mandarinus, the results excluded the Sall4 gene from being the testis-determining factor in this species. We propose that in M. m. mandarinus, sex determination is controlled by another yet unknown gene on the sex chromosomes.     

棕色田鼠罗伯逊易位的研究（简报）

The type of chromosome No. 1 and chromosome number from 53 individuals of Microtus mandarinus have been studied and compared in three sex types: XY, XX, XO. We found that the first pair of autosomes are very unstable, and there are three types: (1) M, M (With a double metacentric chromosome), (2) M, T, T, (With single metacentric chromosome). (3) T, T, T, T (Without metacentric chromosome). The chromosome number of the same sex individuals changes regularly with the type change of chromosome No. 1, that is, the increase of one chromosome in 2n number is always accompanied by the increase of two T and the decrease of one M, and vice versa. The synaptonemal complexes (SCs) of spermatocyte in pachytene nuclei from the males (2n = 51) were analysed by the electron microscopy. The SCs studies demonstrate that there are 23 fully paired autosomal bivalents, XY-bivalent and an autosomal trivalent. This trivalent is formed by one metacentric and two telocentric elements and characterized by the presence of two short side-arms. Meanwhile, all trivalents are in a cis configuration. The study of G-banding also demonstrates that the No. 1 autosome polymorphism is caused by Robertsonian translocation. Robertsonian fission is the main reason of the polymorphism of chromosome No. 1 and of variation of chromosome number in M. mandarinus.     

The origin of the genetical diversity of Microtus mandarinus chromosomes

Here we describe our comparative studies on two types of X chromosomes, namely X(M) and X(SM,) of the mandarin vole (Microtus mandarinus). By chromosome G- and C-banding analysis, we have found that two different types of X chromosomes exist in mandarin voles. The two types of X chromosomes present two different G- and C-banding patterns: the X(M) chromosome is a longer metacentric X chromosome which is C-band negative; and the X(SM) is a shorter submetacentric X chromosome which has one C-band at the centromere and another one at the middle part of the short arm. The X(SM) has 6 G-bands including one on the kinetochore, one in the middle of the short arm, and four on the long arm. The X(M) has 7 G-bands including one on the kinetochore, two on the short arm, and four on the long arm. We have further found that female voles can be grouped into three types based on the composition of the X chromosome but the male voles have only one type. The three female groups are: (1) female voles (X(M)X(SM)), in which the two X chromosomes are different, the longer one is metacentric and the shorter is submetacentric; (2) female vole (X(SM)X(SM)), in which the two X chromosomes are both submetacentric; (3) female vole (X(M)O), in which there is only one X chromosome that is metacentric. Surprisingly, we have never found female voles with X(M)X(M), females with X(SM)O or males with X(M)Y. We hypothesize that the X(SM) chromosome is derived from the X(M) through its breakage and re-joining. The paper also discusses the formation of X(M)O females.     

棕色田鼠胃肠道5-羟色胺细胞的免疫组织化学定位

应用ABC免疫组织化学方法,对棕色田鼠胃肠道内5-羟色胺细胞进行了免疫组织化学定位和形态学观察.结果 表明:5-HTIR细胞在棕色田鼠胃肠道的各段均有分布,其中以十二指肠和直肠段分布密度最高,胃底、胃幽门部、空肠、回肠、盲肠段其次,胃贲门部、胃体、结肠段分布密度最低.5-羟色胺细胞位于胃腺上皮、肠粘膜上皮、肠腺上皮及固有膜,有圆形、椭圆形、梭形、楔形和不规则形,有的还具有胞突.对棕色田鼠胃肠道5-HTIR细胞的分布、形态与功能相适应的特点进行了讨论.     

Sex reversal caused by Mus musculus domesticus Y chromosomes linked to variant expression of the testis-determining gene Sry

When the Y chromosomes from certain populations of Mus musculus domesticus are introduced into the mouse strain C57BL/6 (B6), testis determination can fail, resulting in gonads developing either as ovotestes (with both ovarian and testicular components) or as ovaries. Not all Y(DOM) chromosomes cause sex reversal. Y(DOM) chromosomes are divided into three classes based upon their ability to induce testes in B6. The molecular basis underlying the three Y(DOM) classes is an enigma. The simplest explanation is that they harbor different alleles of the testis-determining gene, Sry. Sequencing of Sry(DOM) genes has indeed identified polymorphisms. However, none were unequivocally linked to the sex-reversal trait. It was concluded that all SRY(DOM) proteins are functionally equivalent. Using a semiquantitative RT-PCR assay, we now show that representatives of the three Y(DOM) classes have variant Sry expression patterns, that severity of sex reversal correlates with Sry mRNA titers, and that genetic correction of the sex reversal results in the upregulation of Sry expression. We propose that the variant Sry expression patterns result from polymorphisms at the site of a putative Sry enhancer.     

Comparison of social interaction and neural activation in the main olfactory bulb and the accessory olfactory bulb between Microtus mandarinus and Microtus fortis

To gain insight into the function of AOB and MOB during different social interaction and in different vole species,the behaviors and neural activation of the olfactory bulbs in social interactions of mandarin voles Microtus mandarinus and reed voles Microtus fortis were compared in the present research.Mandarin voles spent significantly more time attacking and sniffing their opponents and sniffing sawdust than reed voles.During same sex encounters,mandarin voles attacked their opponents for a significantly ...     

Sex determination in Drosophila: the X-chromosomal gene liz is required for Sxl activity.

In Drosophila, females require products of the gene Sxl for sex determination, dosage compensation and fertility. I show here that the X-chromosomal gene liz, located in 4F1 to 4F11 and previously called fs(1)1621, provides maternal and zygotic functions necessary for Sxl activity in germ line and soma. In XX animals, the mutation SxlM1 which was reported to express the female-specific functions of Sxl constitutively can rescue all phenotypes resulting from lack of liz product. XY animals carrying SxlM1 and lacking maternal or zygotic liz activity survive as males with some female traits. A stock was constructed in which the females are liz SxlM1/liz SxlM1 and males liz SxlM1/Y. This shows that SxlM1 is not truly expressed constitutively in animals with an X:A ratio of 0.5, but requires activity of liz for initiation or maintenance.     

Sry: the master switch in mammalian sex determination

SRY, the mammalian Y-chromosomal testis-determining gene, induces male sex determination. Recent studies in mice reveal that the major role of SRY is to achieve sufficient expression of the related gene Sox9, in order to induce Sertoli cell differentiation, which in turn drives testis formation. Here, we discuss the cascade of events triggered by SRY and the mechanisms that reinforce the differentiation of the testes in males while actively inhibiting ovarian development.     

Parental responsiveness negatively correlates with fecal testosterone concentration in male mandarin voles (Microtus mandarinus)

The tradeoff between parental effort and mating effort in male animals may be mediated by testosterone (T). The pattern of association between T and paternal care in birds is consistent with this hypothesis, while it is poorly studied and not universal for mammals. We used the correlation approach to test two predictions of T-mediated tradeoff hypothesis for a biparental vole, Microtus mandarinus: (1) that T levels in males decrease from before pair formation to after birth of the first litter and (2) that paternal responsiveness of males negatively correlates with their T levels. T concentrations were measured in fecal samples collected before pairing and then immediately before behavioral testing on day 5 after birth of the first litter. Both nonpaternal and low paternal males had high initial T that decreased after birth of pups, though the decrease was only significant in low paternal males. In highly paternal males, the initial T was low and did not change after birth. Our results support the predictions of T-mediated tradeoff hypothesis and reveal individual variation in hormone–behavior relationship.     

用C-带和涂染技术检测棕色田鼠Y染色体

采用染色体C 带技术和小鼠整条Y染色体特异探针检测棕色田鼠的Y染色体 ,结果如下 :棕色田鼠雄性个体C 带中期分裂相中 ,X性染色体是亚中部着丝粒染色体 ,在着丝粒处存在着强烈的C阳性带 ,而且在短臂的中间也有一条C阳性带 ,但是没有发现深染的Y染色体。用小鼠整条Y染色体特异探针涂染棕色田鼠的骨髓细胞中期分裂相和间期核 ,以小鼠骨髓细胞中期分裂相和间期核作为对照。涂染结果表明 :棕色田鼠骨髓细胞中期分裂相和间期核涂染信号检出率分别为 0 - 2 %和 3% - 5 % ,两者均呈阴性反应 ,而对照都呈阳性反应。根据实验结果 ,作者认为在棕色田鼠的Y染色体上及整个基因组DNA中不存在小鼠整条Y染色体特异DNA的同源序列 ,其Y染色体上可能没有决定雄性性别的重要基因     

棕色田鼠脑和行为不同发育阶段副嗅球和主嗅球的细胞活动

本文运用免疫组化显示Fos蛋白的方法首次研究了棕色田鼠脑和行为不同发育阶段副嗅球和主嗅球的细胞活动。当不同年龄阶段的幼鼠同时暴露于自己家庭的熟悉底物和另一家庭的陌生底物时 ,嗅闻和呆在自己熟悉底物上的时间较多 ,直到产后 15d、 2 0d和 2 5d时 ,幼鼠探究不同底物的行为显示出显著性差异。脑的大小随着日龄增加而增加 ,但从产后 1到 15d ,脑重、脑宽和嗅球大小随着日龄增加特别显著。当不同日龄幼鼠暴露于陌生底物或者暴露于自己的熟悉底物时 ,从产后 5到 15日龄 ,主嗅球僧帽细胞层、颗粒细胞层、副嗅球僧帽细胞层和颗粒细胞层Fos免疫阳性细胞随着日龄明显增加 ,但直到 15和 30日龄时 ,和对照组相比 ,陌生底物可引起幼鼠主嗅球Fos免疫阳性细胞明显增加 ,从 2 0日龄起 ,陌生底物可引起副嗅球Fos免疫阳性细胞明显增加。主嗅球颗粒细胞层Fos免疫阳性细胞随着日龄的增加从边缘到中心逐渐出现 ,而副嗅球Fos免疫阳性细胞随着日龄的增加从顶部到底部逐渐出现。以上结果说明产后第 1d到 15d左右可能是棕色田鼠脑结构发育的重要阶段 ,而从此以后棕色田鼠主嗅球和副嗅球就具有区别熟悉气味和陌生气味的能力 ,表明棕色田鼠行为、脑发育和细胞活动间有紧密关系     

棕色田鼠脑中雌激素α受体分布和社会互作的两性差异

通过记录分析雌雄棕色田鼠同性间的社会互作并用免疫组织化学方法对雌激素α受体（ERα）在雌雄棕色田鼠脑内的分布进行定位,以揭示ERα在不同性别棕色田鼠社会行为中的调控作用。结果发现：雌性棕色田鼠攻击行为显著多于雄性;雌性棕色田鼠亲密行为明显少于雄性,差异极显著;此外,雌性棕色田鼠的防御行为极显著多于雄性。免疫组织化学结果显示：ERα免疫阳性细胞主要分布在弓状核（ARC）、杏仁内侧核（MeA）、杏仁中央核（Ce）、下丘脑视前区（MPOA）、下丘脑腹内侧核（VMH）和终纹床核（BST）,其中ERα在BST、MPOA、MeA和Ce中的分布存在着极显著性二型性,且雌性田鼠表达的ERα较多;在ARC中的分布也存在显著性二型性,雄性田鼠表达的ERα多于雌性田鼠;ERα在VMH中的分布无明显的性二型性。结果揭示了雌雄棕色田鼠在同性间社会互作中攻击、防御以及亲密行为存在显著差异,而ERα在雌雄棕色田鼠脑内的分布模式也有显著性差异,社会互作和ERα免疫阳性细胞分布的两性差异都呈现单配制鼠类的特征,ERα在大脑分布模式的两性差别和不同种类间的差别可能是单配制啮齿类呈现相关生殖和社会行为的一个重要机制[动物学报54（6）：1020-1028,2008]。     

DNA methylation-mediated control of Sry gene expression in mouse gonadal development

DNA methylation at CpG sequences is involved in tissue-specific and developmentally regulated gene expression. The Sry (sex-determining region on the Y chromosome) gene encodes a master protein for initiating testis differentiation in mammals, and its expression is restricted to gonadal somatic cells at 10.5-12.5 days post-coitum (dpc) in the mouse. We found that in vitro methylation of the 5'-flanking region of the Sry gene caused suppression of reporter activity, implying that Sry gene expression could be regulated by DNA methylation-mediated gene silencing. Bisulfite restriction mapping and sodium bisulfite sequencing revealed that the 5'-flanking region of the Sry gene was hypermethylated in the 8.5-dpc embryos in which the Sry gene was not expressed. Importantly, this region was specifically hypomethylated in the gonad at 11.5 dpc, while the hypermethylated status was maintained in tissues that do not express the Sry gene. We concluded that expression of the Sry gene is under the control of an epigenetic mechanism mediated by DNA methylation.